Various methods are known for introducing DNA, RNA and other polynucleotides and proteins, lipids and other biological substances as foreign substances into target cells. For example, methods that are known for introducing DNA and other genetic material include methods using liposomes (lipofection methods), microinjections methods, electroporation methods, methods using virus vectors, DEAE-dextran transfection, methods using gene guns and the like.
However, it is generally more difficult to introduce foreign substances into plant cells than into animal cells. A plant cell is enveloped by a tough cell wall containing cellulose, and this cell wall presents a barrier to introduction of foreign substances. A common way of increasing the introduction rate of foreign substances into cells is to treat the cells in advance with an enzyme (such as cellulase), converting them into protoplasts. However, the protoplast conversion is a difficult and complex operation. Moreover, skill and care are required when handling cells that have been converted to protoplasts.
One example of this kind of prior art is given in Patent Document 1, which describes using the high working characteristics of laser light to break the polymeric chemical bonds composing the plant cell wall so that a gene or other foreign substance (biological substance) can be introduced into a plant cell. However, the method described in this document still requires an expensive laser irradiation mechanism, and involves complex and difficult operations (laser irradiation treatment, etc.).    Patent Document 1: Japanese Patent Application Laid-open No. 2002-325572